The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; and

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; and

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; and

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; and

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; and

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; andCollaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, China

The Chinese Academy of Sciences Key Laboratory of Innate Immunity and Chronic Disease, School of Life Sciences and Medical Center, University of Science and Technology of China, Hefei, Anhui 230027, China; andCollaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, China

Abstract

Although NK cells are classified as innate immune cells, recent studies have demonstrated the transformation of NK cells into long-lived memory cells that contribute to secondary immune responses in certain mouse models. However, whether NK cells mount an Ag-specific memory response to acute influenza virus infection has not yet been examined. Here, we show that, consistent with previous studies, lung NK cells play an important role in controlling viral proliferation after primary influenza virus infection. However, although lung NK cells display a memory phenotype at the late stage of infection, these cells do not protect mice against secondary influenza virus infection. Interestingly, liver NK cells from influenza virus–infected mice possess a memory phenotype and protect mice against secondary influenza virus infection. Memory-like liver NK cells display a CD49a+DX5− phenotype, and the adoptive transfer of purified liver CD49a+DX5− NK cells into naive mice followed by viral infection results in protective immunity and decreased viral titer. Moreover, we demonstrate that primary inactivated influenza virus induces memory NK cells residing in the liver of Rag1−/− mice. Collectively, these data suggest that liver CD49a+DX5− NK cells remember encountered Ag from influenza virus after primary infection and are more protective upon subsequent infection.

Footnotes

This work was supported by Ministry of Science and Technology of China 973 Basic Science Project Grants 2013CB944902 and 2013CB530506 and National Natural Science Foundation of China Grants 81361120388, 31400783, 91542114, 31300727, and 31300753.